The present invention provides a method for producing coenzyme Q.sub.10.
Coenzyme Q.sub.10 plays an important function as an element of the electron transmission system in an organism. It is known to exhibit an excellent pharmaceutical effect against various diseases. In recent years, it has been clinically employed for curing of cardiac insufficiency by oral administration.
Coenzyme Q.sub.10 has the formula ##STR1##
Coenzyme Q.sub.10 is industrially produced either by a semisynthetic process that uses a material originating in plants, or by a fermentation process that extracts said compound from microbial cells. In the fermentation process, it is necessary to produce microbial cells containing coenzyme Q.sub.10 at a low cost in order to realize an industrially feasible process because the amount of coenzyme Q.sub.10 accumulated in the individual microbial cells is small.
Methods of extracting coenzyme Q.sub.10 from microorganisms, especially from yeast and the like, are disclosed in Japanese Patent Publication No. 8836/1973, Japanese Patent Publication No. 19034/1976 and Japanese Patent Laid-open Publication No. 105288/1977. A process for producing coenzyme Q.sub.10 characterized by the use of higher fatty acid as a substrate in the cultivation of yeast is disclosed in Japanese Patent Publication No. 4758/1975 is known.
In processes utilizing microbial cells, it is usually of importance that the component of the culture medium serving as a primary source of carbon for the growing microbial cells be an inexpensive material. It is an object of the present invention to provide an economic fermentation process for producing coenzyme Q.sub.10, and particularly such a process using an inexpensive carbon source as a component of the culture medium.
The process of producing sulfite pulp from wood produces a waste liquor from the cooking of wood referred to industrially and hereinafter as SWL. SWL has been employed in the production of yeast of the type used as a food and also as a feed component for animals. Recently SWL has been used as a source material for the production of a particular yeast belonging to the genus Torula from which useful (active) components such as nucleic acid and glutathione are extracted. SWL contains saccharoid, acetic acid and alcohols that are useful for the cultivation of yeast. However, SWL also contains many substances, such as sulfurous acid, decomposition products of lignin, furfural, formic acid and loosely combined sulfite, which inhibit the growth of yeasts. As a consequence, SWL is generally a substance having a poor capability as a culture medium for yeasts in general. The specific types of yeast which can grow in a culture medium containing SWL as a main carbon source are limited. Only the aforesaid genus Torula and the like are cultivated in an SWL-containing medium on an industrial scale.
Because of the inexpensive nature of SWL, we have endeavored to provide a process for producing coenzyme Q.sub.10 from a microorganism which can assimilate SWL.